Damage to the asphalt of a road surface can occur through oxidation of the asphalt surface, repeated impaction by vehicular traffic and/or adverse weather conditions.
There are a number of different systems and methods currently used to repair defects, such as potholes, in an asphalt surface. The procedure providing the most durable repair that is currently available involves providing a “clean” edge to the defect, for example by saw cutting around the damaged area, in order to provide vertical edges to the defect. Loose debris is then removed from the defect area, after which a bond material is applied to the base and the sides of the hole. An asphalt filler material (typically a “hot-mix” material) is introduced to the hole and is then compacted and allowed to cool.
However, despite being the most durable repair, the seam between the old asphalt and the new asphalt is a weak point within the repair, which leads to the new asphalt filler material separating from the old asphalt over time. As such, the lifetime of such a repair is typically no longer than 2 to 3 years, after which the defect reappears and the surface requires repairing once more.
According to the Annual Local Authority Road Maintenance Survey 2015 by the Asphalt Industry Alliance, around 2,670,350 potholes were repaired in the UK during 2014 at a total cost of £144.3 million.
It is estimated that it will take around 13 years and cost in the region of £12.1 billion to repair the current backlog of potholes in roads in the UK alone.
However, this estimate is for repairing current potholes and does not take into account the re-occurrence of the potholes due to the limited lifetime of pothole repairs. Therefore, due to the reoccurrence of potholes after such a short time-span, the costs of repairing the roads will increase substantially.
UK application number GB 2418444 describes a road heater system for use in the repair of roads using a Hot-In-Place Recycling technique. The system heats the surface of the road area comprising a defect with an infrared heat source, after which new asphalt filler material is added and the filler material is compacted.
However, the applicants have found that a large amount of oxidation occurs within the asphalt surface when using such a system resulting in a weak and brittle asphalt surface, which in turns lead to the rapid reoccurrence of the pothole defect.
The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.
The present invention provides an improved system and method for repairing defects in an asphalt surface. The system of the invention may also be used for other processes requiring the heating of an asphalt surface.
According to the present invention, there is provided an asphalt heater system, comprising a source of a flow of inert gas, a heater for heating the flow of inert gas and means for directing the flow of heated inert gas to the asphalt surface, wherein the means for directing the flow of heated inert gas to the asphalt surface is a lance.
Preferably, the inert gas is nitrogen.
Advantageously, the source of a flow of inert gas is selected from the group consisting of a pressure swing adsorption nitrogen generator and compressed gas, preferably wherein the compressed gas is nitrogen.
Preferably, the system further comprises an air compressor for supplying air to the pressure swing adsorption nitrogen generator.
Conveniently, the pressure swing adsorption nitrogen generator is configured to provide a flow of nitrogen and a separate flow of oxygen within the system.
Advantageously, the system further comprises a burner or an electrical heater for supplying energy to the heater.
Preferably, the system further comprises means to supply the flow of oxygen to the burner.
Conveniently, the heater is configured to heat the inert gas flow to a temperature of from about 40° C. to about 650° C., for example from about 100° C. to about 500° C., such as from about 200° C. to about 450° C., for example from about 300° C. to about 400° C. and preferably of about 400° C.
According to another aspect of the invention, there is provided the use of a system as detailed above in repairing a defect in an asphalt surface.
According to an additional aspect of the invention, there is provided the use of a system as detailed above in removing indicia from an asphalt surface.
According to a further aspect of the invention, there is provided a method for repairing a defect in an asphalt surface, wherein the method comprises the steps of:                providing a flow of inert gas;        heating the flow of inert gas;        heating the asphalt surface using the flow of heated inert gas; and        providing a filler material to the defect in the road surface, wherein the asphalt surface is heated using a lance.        
Preferably, the inert gas is nitrogen.
Advantageously, the asphalt surface is heated to a temperature of greater than about 40° C., for example to temperatures between about 80° C. to about 400° C., such as between about 100° C. and about 200° C., preferably the asphalt surface is heated to temperatures of between about 100° C. and about 150° C.
Preferably, the method comprises the use of a pressure swing adsorption nitrogen generator or compressed nitrogen to provide the flow of nitrogen.
Conveniently, the pressure swing adsorption generator also provides a flow of oxygen.
Advantageously, the flow of inert gas is heated by the use of a burner or an electrical heater.
Preferably, the flow of oxygen is supplied to the burner.
Conveniently, the inert gas is heated to a temperature of from about 40° C. to about 650° C., for example from about 100° C. to about 500° C., such as from about 200° C. to about 450° C., for example from about 300° C. to about 400° C. and preferably to about 400° C.
Advantageously, the filler material is an asphalt, bituminous or aggregate material.
Preferably, the filler material is mechanically agitated.